Machining method for controlling carburizing and quenching deformation of thin-wall sleeve gear

Abstract

The invention discloses a processing method for controlling carburizing and quenching deformation of a thin-wall sleeve gear, which is characterized in that the thin-wall sleeve gear is slowly cooled along with a furnace in a vacuum environment after carburizing, deformation caused by thermal stress is favorably reduced, and then a solid carburizer is adopted for boxing protection, so that no oxidation and no decarburization of parts can be ensured; the part which is expanded after being heated is quickly sleeved into the cold-state quenching mold to restrain the free shrinkage of the part, so that the quenching deformation can be effectively controlled, and the dimensional stability of the part after being quenched is ensured; after the part is cooled to the room temperature, cooling continues, heat preservation is conducted for preset time, then air cooling is conducted, residual austenite can be reduced, and the hardness and abrasion resistance of the carburized surface are improved; and finally, the thin-wall sleeve gear is subjected to air cooling after low-temperature heating and heat preservation for preset time, quenching internal stress can be reduced, and brittleness is reduced. According to the method, carburizing and quenching deformation of the thin-wall sleeve tooth is remarkably reduced, the stability of the machining size of the part is improved, the wall thickness of the part does not need to be thickened, machining deformation is reduced, and the machining quality of the part is improved.

Description

Technical Field

[0001] The invention relates to the technical field of thin-walled sleeve gear processing, in particular to a processing method for controlling carburizing and quenching deformation of thin-walled sleeve gear. Background Art

[0002] Gears are wheel-shaped mechanical parts that transmit torque by meshing teeth, and can achieve functions such as changing speed and torque, changing movement direction and changing movement form. In order to achieve high power-to-weight ratio and compact structure, the gear parts used to transmit torque in aircraft engines require high hardness and high wear resistance on the working tooth surface, good contact fatigue performance, high strength and toughness and high rigidity in the non-permeable parts. Therefore, it is generally required that the tooth surface of the parts be carburized and the parts be quenched and heat treated as a whole. Such processing requirements make it very difficult to control the deformation during heat treatment. In addition, the parts are also required to have high dimensional accuracy, lightweight structure, stable processing quality and good working reliability.

[0003] like Figure 1 As shown in the figure, a certain type of aircraft engine has designed a thin-walled sleeve gear to achieve the power turbine torque output. The upper and lower ends of the part are two internal spline integral sleeve gear structures, the maximum radial dimension does not exceed 100mm, and the selected material is 16Cr3NiWMoVNb carburized steel. The two internal spline tooth profiles are required to be carburized. The wall thickness of the thinnest part of the part is only 2mm, and the wall thickness of the thickest part of the tooth is only 4.5mm. The two internal spline modules are small module tooth thickness internal spline structure, the tooth span spacing tolerance requirement is 0.066mm, and the upper and lower end face parallelism requirement is 0.02mm. The part is a thin-walled internal spline tooth type precision carburized part, and the carburizing quality and dimensional accuracy control requirements are high. The existing processing route of the thin-walled sleeve gear is as follows: Figure 2 As shown, the tooth shape of the part is processed by the gear shaping method. Since the part is a small-tooth-thickness internal spline gear structure, it is difficult to grind the gear. In addition, in order to retain the high-hardness and high-wear-resistant carburized layer, the gear shaping will process the tooth profile parameters to the final size according to the design requirements. After carburizing and quenching, only the tooth profile is ground and trimmed, that is, the tooth surface is processed with little or no allowance after heat treatment. Therefore, in order to prevent the deformation of thin-walled parts during carburizing and quenching, the existing processing method will increase the external wall thickness of the part by 2mm before carburizing and quenching according to the structural characteristics of the part to reduce the heat treatment deformation, and then use the low-pressure vacuum carburizing process to form a high-quality carburized layer. The quenching uses a controlled atmosphere to protect the overall heating and rapid quenching oil quenching process to achieve the overall quenching quality and deformation control of the part.

[0004] However, the inventors of the present application discovered during the actual production process that the deformation of different parts after carburizing and quenching varies greatly. For example, the maximum deformation of the roundness of the teeth of some parts is 0.16 mm, and the maximum deformation of the end face flatness is 0.08 mm. The radial size reduction of different parts varies greatly, resulting in poor dimensional stability of parts in the same batch after processing and a low pass rate in parts inspection. In addition, after the outer wall thickness of the parts is thickened and hardened by quenching, it is difficult to remove the machining allowance, and the machining stress needs to be increased in the subsequent machining process, resulting in machining deformation, which causes the teeth of some parts to be deformed and scrapped, and the stability of the parts processing quality cannot be guaranteed. Summary of the invention

[0005] The invention provides a processing method for controlling carburizing and quenching deformation of thin-walled sleeve teeth, which can significantly reduce the carburizing and quenching deformation of thin-walled sleeve teeth and improve the processing dimensional stability and processing quality of parts.

[0006] According to one aspect of the present invention, a processing method for controlling carburizing and quenching deformation of a thin-walled sleeve tooth is provided, comprising the following contents:

[0007] Carburizing treatment: low-pressure vacuum pulse carburizing is performed on thin-walled sleeve teeth, and then slowly cooled in the furnace after carburizing;

[0008] Quenching treatment: put the thin-walled sleeve gear into a solid carburizing agent protection box, seal it and then heat it. After heating, quickly put the thin-walled sleeve gear into a cold quenching mold for overall oil spray cooling and quenching.

[0009] Cold treatment: Continue cooling the thin-walled sleeve gear, keep warm for a preset time, and then air cool;

[0010] Tempering treatment: The thin-walled sleeve gear is heated at low temperature and kept warm for a preset time, then air-cooled.

[0011] Furthermore, the carburizing step includes the following contents:

[0012] Place the thin-walled sleeve gear in a vacuum carburizing furnace for low-pressure vacuum pulse carburizing. After evacuation, raise the temperature to 650℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 850℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 930℃±10℃, keep it warm for 30 to 50 minutes, and then start automatic carburizing with acetylene. After carburizing, cool down to ≤100℃ and take it out of the furnace.

[0013] Furthermore, the quenching step includes the following:

[0014] Place the thin-walled sleeve gear with the large end facing downward into a solid carburizing agent protection box and seal it. Then heat the protection box in a box-type electric furnace. Keep it at 650℃±10℃ for 35 to 45 minutes, then raise the temperature to 920℃±10℃ with the furnace and keep it for 40 to 60 minutes. Then quickly clamp out the parts one by one and put them into a cold quenching mold. Spray oil on the inner and outer surfaces of the thin-walled sleeve gear on a quenching press to cool and quench. Continue spraying oil until the thin-walled sleeve gear cools to room temperature.

[0015] Furthermore, the quenching mold includes an upper die, a quenching core die, an oil injection base, an oil retaining ring and a demolding base. The small end of the upper die is connected and fixed to the lower pressing mechanism of the quenching press, and the large end of the upper die is evenly distributed with a plurality of pressing claws along the circumference, which are used to evenly press the middle outer plane of the thin-walled sleeve gear to control the end face flatness. The oil injection base is connected and fixed to the movable base of the quenching press, and is used to communicate with the oil injection oil circuit of the quenching press to quickly spray out quenching oil. The quenching core die is installed on the oil injection base, and the thin-walled sleeve gear is sleeved on the quenching core die. The quenching core die is used to fix the thin-walled sleeve gear, divert the quenching oil and control the roundness of the tooth portion of the thin-walled sleeve gear. The oil retaining ring is installed in the annular groove of the oil injection base, and is used to maintain a fixed quenching oil level height so that the thin-walled sleeve gear is completely immersed in the quenching oil. The demolding base is used to perform demolding operations.

[0016] Furthermore, an oil injection hole is opened in the middle of the oil injection base and passes through it from top to bottom. A plurality of first oil guide grooves are evenly distributed radially on the middle plane of the oil injection base, and the plurality of first oil guide grooves are connected to the oil injection hole. The central inner hole of the quenching core mold is aligned with the oil injection hole. During the quenching process, the quenching oil is sprayed upward from the oil injection hole. A part of the quenching oil flows out through the plurality of first oil guide grooves and flows to the outside of the thin-walled sleeve tooth to cool its outer wall surface. Another part of the quenching oil is sprayed out through the central inner hole of the quenching core mold and fills the inner cavity of the thin-walled sleeve tooth to cool its inner wall surface.

[0017] Furthermore, the central inner hole of the upper die is aligned with the central inner hole of the quenching core die, and a plurality of second oil guide grooves inclined downward are evenly distributed radially on the middle plane of the upper die, the number of the second oil guide grooves is the same as the number of the pressure claws, and the end position of each second oil guide groove is aligned with the pressure claw, and part of the quenching oil sprayed from the central inner hole of the quenching core die flows in sequence through the central inner hole of the upper die, the plurality of second oil guide grooves and the plurality of pressure claws to the outer wall surface of the thin-walled sleeve tooth, so as to achieve rapid and uniform cooling of the outer wall surface.

[0018] Furthermore, the upper end surface of the quenching core mold is evenly distributed with a plurality of stepped third oil guide grooves along the radial direction, so that the quenching oil can flow stably along the inner wall surface of the thin-walled sleeve gear, thereby achieving uniform and stable cooling of the inner wall surface of the thin-walled sleeve gear.

[0019] Furthermore, when the thin-walled sleeve gear is cooled to room temperature, the thin-walled sleeve gear and the quenching core mold are taken out, the thin-walled sleeve gear is supported on the upper end face step of the demolding base, and downward pressure is slowly applied to the top plane of the quenching core mold to withdraw the quenching core mold and complete the demolding operation.

[0020] Furthermore, the cold treatment step includes the following contents:

[0021] After the thin-walled sleeve gear is cooled to room temperature, it is transferred to a low-temperature box that has been pre-cooled to -70°C and kept for 2h to 2.5h before being taken out of the oven and naturally returned to room temperature.

[0022] Furthermore, the tempering step includes the following contents:

[0023] Place the thin-walled sleeve gear in a pit-type electric furnace and heat it to 270℃±10℃. Keep it warm for 2h~2.5h, then take it out and air cool it.

[0024] The present invention has the following beneficial effects:

[0025] The processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth of the present invention is to slowly cool the parts in a vacuum environment after low-pressure vacuum carburizing, which is helpful to reduce the deformation caused by thermal stress, and at the same time can greatly ensure that the surface of the parts is free of oxidation and the original color of the metal can be maintained; then, solid carburizing agent is used for packaging and protection, which can ensure that the parts are free of oxidation and decarburization, and the principle of thermal expansion and contraction of metal is used to quickly put the parts after thermal expansion into a cold quenching mold to restrain the free contraction of the parts, which can effectively control the quenching deformation and ensure the dimensional stability of the parts after quenching; when the parts are cooled to room temperature, they are further cooled, and air-cooled after being kept warm for a period of time, so that the residual austenite in the carburized layer that has not been transformed at room temperature can be further transformed into martensite, and the hardness and wear resistance of the carburized surface can be improved; finally, the thin-walled sleeve teeth are heated and kept warm for a preset time and then air-cooled, which can reduce the quenching internal stress, reduce brittleness, stabilize the structure and size, and at the same time maintain the high hardness and high wear resistance of the carburized layer surface to improve toughness. The processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth of the present invention can significantly reduce the carburizing and quenching deformation of thin-walled sleeve teeth, improve the dimensional stability of parts processing, and does not require thickening of the wall thickness of the parts, which can reduce the processing stress in the machining process, reduce machining deformation, and improve the processing quality of parts.

[0026] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 It is a schematic diagram of the structure of a thin-walled sleeve gear;

[0029] Figure 2 It is a schematic diagram of the existing processing route of thin-walled sleeve gear;

[0030] Figure 3 It is a schematic flow chart of a processing method for controlling carburizing and quenching deformation of thin-walled sleeve teeth according to a preferred embodiment of the present application;

[0031] Figure 4 It is a schematic diagram of the cross-sectional structure of the quenching die of the preferred embodiment of the present application during quenching;

[0032] Figure 5 It is a schematic cross-sectional structure diagram of the quenching die during demoulding of the preferred embodiment of the present application;

[0033] Figure 6 1 is a schematic diagram of the top structure of the upper die of the preferred embodiment of the present application;

[0034] Figure 7 yes Figure 6 Schematic diagram of the cross-section structure cut from AA;

[0035] Figure 8 It is a schematic diagram of the top view of the quenching core mold of the preferred embodiment of the present application;

[0036] Fig. 9 yes Figure 8 Schematic diagram of the cross-section structure cut from BB.

[0037] Description of Reference Numerals

[0038] 1. Upper die; 2. Quenching core die; 3. Oil injection base; 4. Oil retaining ring; 5. Demolding base; 11. Pressing claw; 12. Second oil guide groove; 31. Oil injection hole; 32. First oil guide groove; 21. Third oil guide groove. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] Reference Figure 3 The preferred embodiment of the present application provides a processing method for controlling carburizing and quenching deformation of thin-walled sleeve teeth, comprising the following contents:

[0041] Step S1: Carburizing treatment: low-pressure vacuum pulse carburizing is performed on the thin-walled sleeve gear, and then slowly cooled in the furnace after carburizing;

[0042] Step S2: quenching treatment: the thin-walled sleeve gear is placed in a solid carburizing agent protection box and sealed before being heated. After the heating is completed, the thin-walled sleeve gear is quickly inserted into a cold quenching mold for overall oil spray cooling and quenching;

[0043] Step S3: Cold treatment: continue cooling the thin-walled sleeve gear, keep it warm for a preset time, and then air cool it;

[0044] Step S4: Tempering treatment: The thin-walled sleeve gear is heated at a low temperature and kept warm for a preset time, and then air-cooled.

[0045] It can be understood that the processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth in this embodiment is to slowly cool the parts in a vacuum environment after low-pressure vacuum carburizing, which helps to reduce the deformation caused by thermal stress, and at the same time can greatly ensure that the surface of the parts is free of oxidation and the original color of the metal can be maintained; then, the solid carburizing agent is used for packaging and protection, which can ensure that the parts are free of oxidation and decarburization, and the principle of thermal expansion and contraction of metal is used to quickly put the parts that have expanded due to heat into a cold quenching mold to constrain the free shrinkage of the parts, which can effectively control the quenching deformation and ensure the dimensional stability of the parts after quenching; when the parts are cooled to room temperature, they are continued to be cooled, and air-cooled after being kept warm for a period of time, the residual austenite in the carburized layer that has not been transformed at room temperature can be further transformed into martensite, which can improve the hardness and wear resistance of the carburized surface; finally, the thin-walled sleeve teeth are heated and kept warm for a preset time and then air-cooled, which can reduce the quenching internal stress, reduce brittleness, stabilize the structure and size, and at the same time maintain the high hardness and high wear resistance of the carburized layer surface to improve toughness. The processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth of the present invention can significantly reduce the carburizing and quenching deformation of thin-walled sleeve teeth, improve the dimensional stability of parts processing, and does not require thickening of the wall thickness of the parts, which can reduce the processing stress in the machining process, reduce machining deformation, and improve the processing quality of parts.

[0046] Wherein, in the step S1, the carburizing step includes the following contents:

[0047] Place the thin-walled sleeve gear evenly and flatly in the material frame, and then place the material frame in a vacuum carburizing furnace for low-pressure vacuum pulse carburizing. After evacuation, raise the temperature to 650℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 850℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 930℃±10℃, keep it warm for 30 to 50 minutes, and then start automatic carburizing with acetylene. The carbon potential can be set to 0.95~1.15%. After carburizing, cool it to ≤100℃ and take it out of the furnace.

[0048] It can be understood that by adopting two-stage preheating at 650℃ and 850℃, the parts can be heated more fully and the temperature of each part can be evenly distributed, which is beneficial to reducing the deformation difference of parts during the carburizing process. By adopting the vacuum carburizing method, the surface quality of the parts is good, and the carburized layer does not produce internal oxidation, which helps to improve the fatigue strength of the parts and can greatly improve the reliability and performance of the parts. In addition, slow cooling with the furnace after carburizing helps to reduce the deformation of thin-walled sleeve teeth. At the same time, it can greatly ensure that the surface of the parts is not oxidized and the original color of the metal can be maintained.

[0049] In addition, in step S2, the quenching step includes the following contents:

[0050] Place the thin-walled sleeve gear with the large end facing downward into a solid carburizing agent protection box and seal it. Then heat the protection box in a box-type electric furnace. Keep it at 650℃±10℃ for 35 to 45 minutes, then raise the temperature to 920℃±10℃ with the furnace and keep it for 40 to 60 minutes. Then quickly clamp out the parts one by one and put them into a cold quenching mold. Spray oil on the inner and outer surfaces of the thin-walled sleeve gear on a quenching press to cool and quench. Continue spraying oil until the thin-walled sleeve gear cools to room temperature.

[0051] Specifically, after the carburizing treatment of the parts is completed, the large end of the thin-walled sleeve gear is placed downward into a solid carburizing agent protection box for sealing, and then the protection box is placed in a box-type electric furnace for heating and insulation. After being kept at 650℃±10℃ for 35 to 45 minutes, the temperature is raised to 920℃±10℃ with the furnace and kept for 40 to 60 minutes. After austenitization, the parts are quickly clamped out and put into the cold quenching mold one by one, and the whole oil spray cooling quenching is realized on the quenching press to cause martensitic structure transformation. The fixed carburizing agent box protection is used during the quenching process to ensure that the parts are not oxidized or decarburized during the quenching process, and the principle of thermal expansion and contraction of metals is used to quickly put the parts that have been expanded by heat into the cold quenching mold to constrain the free contraction of the parts, which can effectively control the quenching deformation and ensure the dimensional stability of the parts after quenching.

[0052] Among them, Figures 4 to 9As shown, the quenching mold includes an upper die 1, a quenching core die 2, an oil injection base 3, an oil retaining ring 4 and a demoulding base 5. The small end of the upper die 1 is connected and fixed to the lower pressing mechanism of the quenching press. The large end of the upper die 1 is evenly distributed with a plurality of pressing claws 11 along the circumferential direction, which are used to evenly press the middle outer plane of the thin-walled sleeve gear to control the end surface flatness. The oil injection base 3 is connected and fixed to the movable base of the quenching press, and is used to communicate with the oil injection oil circuit of the quenching press to quickly spray out the quenching oil. The quenching core die 2 is installed on the oil injection base 3, and the thin-walled sleeve gear is sleeved on the quenching core die 2. The quenching core die 2 is used to fix the thin-walled sleeve gear, divert the quenching oil and control the roundness of the tooth portion of the thin-walled sleeve gear. The oil retaining ring 4 is installed in the annular groove of the oil injection base 3 to maintain a fixed quenching oil level so that the thin-walled sleeve gear is completely immersed in the quenching oil. The demoulding base 5 is used for demoulding operation. Among them, the demolding base 5 is a cylindrical structure with a small step on its upper end face, which is used to position and support the end face of the part. After quenching and cooling, the upper end face of the quenching core mold 2 is gently pressed downward to separate the quenching core mold 2 from the part, thereby realizing the demolding process. The demolding base 5 is made of carbon steel or alloy steel.

[0053] Specifically, in a specific embodiment of the present invention, the outer circumference of the small end of the upper die 1 is an external thread to achieve connection and fixation with the pressing mechanism of the quenching press, and the large end of the upper die 1 is evenly distributed with eight pressing claws 11 along the axial direction, which are used to evenly press the middle outer plane of the thin-walled sleeve gear, so that the end surface flatness can be controlled during the quenching process. The material of the upper die 1 can be selected from carbon steel or alloy steel. Of course, the number of the pressing claws 11 can be set according to actual needs and is not specifically limited here.

[0054] Since the upper die 1 adopts an integral pressure claw structure evenly distributed along the radial direction, the circumferential pressure claw 11 directly acts on the deformation plane of the part to be controlled, while the previous pressure plate structure only acts on the small uppermost plane of the part and does not directly act on the deformation plane to be controlled. In addition, the circumferential multi-point uniform contact and pressing method can contact the workpiece surface more evenly, thereby controlling the plane deformation more accurately. The upper die 1 of the present invention can control the end face flatness to 0.04mm after quenching processing by a press, while the end face flatness of the upper die with the previous pressure plate structure is controlled at 0.10mm, and the end face flatness control level is improved by 60%.

[0055] The oil injection base 3 is fixed to the movable base of the quenching press. The middle of the oil injection base 3 is provided with an oil injection hole 31 which runs through from top to bottom, and is used to communicate with the oil injection oil circuit of the quenching press to quickly spray out the quenching oil. When the oil injection base 3 is rotated until the oil injection hole 31 is aligned and connected with the oil injection oil circuit of the quenching press, the quenching oil sprayed by the quenching press can be quickly sprayed upward through the oil injection hole 31. The lower end cylinder of the quenching mandrel 2 is installed in the oil injection hole 31 of the oil injection base 3, and the thin-walled sleeve gear is sleeved on the quenching mandrel 2. By designing a suitable mandrel diameter size, the deformation of the two internal splines of the part can be controlled. Moreover, the mandrel quenching process is a cold size temperature, and the diameter size of the mandrel constrains the free contraction of the part, thereby controlling the roundness size of the part's tooth portion. As a preferred embodiment, the diameter size of the part's tooth portion constraint on the mandrel is 0.05mm to 0.08mm larger than the difference in the minor diameter size of the tooth, so that the optimal tooth portion roundness can be obtained. In addition, in order to ensure the dimensional stability and service life of the mold, the quenching core mold 2 is made of carbon steel or alloy steel and the contact surface is carburized and quenched.

[0056] In addition, the quenching core mold 2 can also play a role in diverting the quenching oil, so that the quenching oil can flow to the inside and outside of the thin-walled sleeve gear respectively, so as to cool the inner wall and outer wall of the thin-walled sleeve gear at the same time, so as to obtain a better cooling effect and further reduce the quenching deformation. For example, the middle part of the oil injection base 3 is provided with an oil injection hole 31 that penetrates up and down, and the middle plane of the oil injection base 3 is evenly distributed with a plurality of first oil guide grooves 32 along the radial direction, and the plurality of first oil guide grooves 32 are all connected with the oil injection hole 31, and the central inner hole of the quenching core mold 2 is aligned with the oil injection hole 31. During the quenching process, the quenching oil is sprayed upward from the oil injection hole 31, a part of the quenching oil flows out through the plurality of first oil guide grooves 32 and flows to the outside of the thin-walled sleeve gear to cool its outer wall surface, and another part of the quenching oil is sprayed through the central inner hole of the quenching core mold 2 and fills the inner cavity of the thin-walled sleeve gear to cool its inner wall surface. In addition, an annular groove is provided on the oil injection base 3, and the oil retaining ring 4 is installed in the annular groove. The material of the oil injection base 3 can be carbon steel or alloy steel.

[0057] Optionally, the central inner hole of the upper die 1 is aligned with the central inner hole of the quenching core die 2, and a plurality of downwardly inclined second oil guide grooves 12 are evenly distributed radially on the middle plane of the upper die 1, the number of the second oil guide grooves 12 is the same as the number of the pressing claws 11, and the end position of each second oil guide groove 12 is aligned with the pressing claw 11. Part of the quenching oil sprayed from the central inner hole of the quenching core die 2 flows to the outer wall surface of the thin-walled sleeve tooth through the central inner hole of the upper die 1, the plurality of second oil guide grooves 12 and the plurality of pressing claws 11 in sequence, so as to achieve rapid and uniform cooling of the outer wall surface.

[0058] It can be understood that, since the quenching oil has a relatively high viscosity and has a certain adhesion to the contact surface, the quenching oil in the second oil guide groove 12 with a slope has a good flow effect and a fast oil flow cycle compared to the existing flat groove structure due to the drainage effect of the slope, and the outer wall can be quickly cooled. At the same time, since the quenching oil in the existing flat groove structure mainly flows out along the circumference of the groove, the quenching oil is relatively dispersed on the surface of the workpiece, that is, the amount of quenching oil on the surface of the workpiece is small, so the cooling effect is poor. However, in the present invention, under the action of the gravity and adhesion of the quenching oil, the quenching oil mainly flows downward along the circumferential pressure claw 11 to the outside of the part, and the quenching oil is more concentrated on the outer surface of the part. The more quenching oil flows on the surface of the workpiece and the faster the flow, the better the quenching cooling effect.

[0059] Preferably, the upper end surface of the quenching core mold 2 is evenly distributed with eight stepped third oil guide grooves 21 along the radial direction, so that the quenching oil can flow stably along the inner wall surface of the thin-walled sleeve gear to achieve uniform and stable cooling of the inner wall surface of the thin-walled sleeve gear.

[0060] It can be understood that the quenching core mold 2 adopts a stepped oil guide groove structure, and is designed with eight stepped oil guide grooves evenly distributed along the circumference of the inner wall of the part, so that the quenching oil can always flow and cool continuously and stably along the inner wall of the workpiece, and the stepped structure oil guide groove can keep more quenching oil flowing on the inner surface of the part. Compared with the existing radial straight groove structure, the oil circuit is longer, the quenching oil flow time is longer, the heat exchange with the inner surface of the part is more sufficient and uniform, and the cooling and heat dissipation effect is better.

[0061] It can be understood that the quenching die of the present invention adopts an upper die 1 with an inclined oil guide groove and an integral pressure claw structure, and a quenching core die 2 with a stepped oil guide groove, so that the amount of quenching oil to keep the inner and outer surfaces of the workpiece cooled is greater than that of the existing pressure plate and the straight groove structure along the radial direction, and the cooling and heat dissipation are more sufficient and the cooling is more uniform. In addition, the quenching oil flows upward through the first oil guide groove 32 of the oil injection base 3, and the quenching oil flows downward rapidly through the second oil guide groove 12 and the pressure claw 11 on the upper die 1, so that the quenching oil can flow from the upper end and the lower end to the middle on the outer wall of the part at the same time, which greatly improves the cooling speed and cooling effect of the outer wall of the part, and improves the cooling uniformity of the upper and lower ends of the outer wall. In addition, the outer wall surface is rapidly cooled by the oblique guide grooves of the upper die 1 and the pressure claws 11, and the outer wall surface is stably cooled by the stepped oil guide grooves of the quenching core die 2, so that the outer wall surface of the part is rapidly cooled and contracted, while the inner wall surface is stably cooled and contracted, which is beneficial to reducing the roundness deformation of the teeth on the inner wall surface. The roundness of the teeth of the workpiece quenched by this scheme can be controlled at 0.06mm, compared with the existing pressure plate and the radial straight groove structure scheme whose roundness is controlled at 0.12mm, the roundness control level of the workpiece is improved by 50%.

[0062] It can be understood that the quenching process specifically includes the following contents:

[0063] 1. Preparation:

[0064] Before quenching, the upper die 1 is connected and fixed to the pressing mechanism of the quenching press through the external thread at the small end of the die, and the upper die 1 is kept directly above the center hole of the oil injection base 3 to ensure that the upper die 1 moves up and down to achieve alignment and clamping functions; the oil injection base 3 is kept horizontally fixed on the movable base of the quenching press, and the oil injection base 3 is fixed to the movable base of the quenching press to achieve circumferential rotation function; then the quenching core mold 2 is placed at the oil injection hole 31 of the oil injection base 3 to position it, and the oil retaining ring 4 is sleeved in the annular groove of the oil injection base 3 to maintain a fixed quenching oil level height, ensuring that all parts are immersed in the quenching oil for cooling, and the excess oil can overflow along the top edge of the oil retaining ring 4 to achieve the circulation of the quenching oil. The quenching press and the quenching die can be combined to realize the quenching operation, and automatic quenching can be realized after the quenching press is modified.

[0065] 2. Quenching operation:

[0066] After the heating and insulation of the parts are completed, the upper end surface of the parts is clamped from the solid carburizing agent protection box with quenching pliers, the parts are quickly taken out and aligned with the core mold, and the parts are inserted into the quenching core mold 2. Then, the quenching press handle is turned to turn the oil injection base 3 to the oil injection hole 31 to connect with the oil injection oil circuit of the quenching press. At the same time, the movable base of the quenching press presses the oil injection motor pressure switch, starts the oil injection motor to achieve rapid and continuous oil injection, and turns the handle to press the pressing mechanism of the quenching press by gravity. The start switch drives the cylinder to automatically move the upper die 1 downward, and the eight pressure claws 11 evenly distributed around the upper die 1 are used to evenly press the outer plane of the middle part of the part to maintain the clamping constraint to control the end surface flatness. The quenching oil is sprayed upward from the oil spray hole 31 in the middle of the oil spray base 3, and after the diversion effect of the quenching core mold 2, a part of it flows along the first oil guide groove 32 to the outer surface of the part, and the other part quickly flows into the inner cavity of the part along the central inner hole of the quenching core mold 2; a part of the quenching oil in the inner cavity passes through the eight radially uniformly distributed second oil guide grooves 12 and the pressing claws 11 in the middle of the upper pressing die 1, so that the quenching oil can flow and cool quickly on the outer surface of the part, and the other part of the quenching oil flows downward from the middle of the part through the eight radially uniformly distributed third oil guide grooves 21 on the outer surface of the quenching core mold 2. Flow, so that the quenching oil can flow stably on the inner surface of the part; through the oil retaining ring 4, the quenching oil around the part is maintained at a fixed liquid level to ensure that the part is completely immersed in the oil. At the same time, the continuously flowing oil flows rapidly on the inner and outer surfaces of the part to achieve overall quenching cooling, and the part quickly shrinks until it contacts the surface of the quenching core mold 2, which restricts the part from further shrinking, stabilizes the circumferential size of the tooth part, and controls the roundness of the part; the quenching oil overflows from the top edge of the oil retaining ring 4 and flows back to the oil storage tank of the quenching press to achieve continuous circulation cooling, and the quenching operation is performed on each part according to the above method.

[0067] 3. Core stripping operation:

[0068] After the part is continuously sprayed with oil for cooling for 1min to 1.5min and cooled to near room temperature in the quenching press mold, lift the handle of the quenching press upwards, and the upper die 1 automatically moves upwards to the original position to loosen the part, and the movable base of the quenching press is rotated back to the initial position. The part is kept in a compressed state with the quenching core mold 2 due to cooling shrinkage. The part and the quenching core mold 2 are taken out as a whole, and the large end face of the thin-walled sleeve gear is supported on the upper end face step of the demolding base 5. The top plane of the quenching core mold 2 is slowly pressed down to withdraw the quenching core mold 2 to complete the demolding operation.

[0069] In addition, in step S3, the cold treatment step includes the following contents:

[0070] After the thin-walled sleeve gear is cooled to room temperature, it is transferred to a low-temperature box that has been pre-cooled to -70°C and kept for 2h to 2.5h before being taken out of the oven and naturally returned to room temperature.

[0071] It can be understood that the present invention can fully eliminate the residual austenite in the carburized layer by cold treatment at -70°C after quenching treatment, thereby ensuring the stability of the carburized layer structure and the high hardness requirement.

[0072] In addition, in step S4, the tempering step includes the following contents:

[0073] Lay the thin-walled sleeve gear flat in a basket and put it into a pit-type electric furnace to heat it to 270℃±10℃. After keeping it warm for 2h~2.5h, hang the basket out and air cool it.

[0074] It can be understood that the present invention adopts 270°C tempering after cold treatment, which can fully eliminate quenching internal stress, reduce quenching martensite brittleness, stabilize the structure and size, and at the same time maintain high hardness and high wear resistance of the carburized layer surface, and the toughness is also improved.

[0075] It can be understood that the processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth of the present invention adopts vacuum carburizing followed by slow cooling in the furnace and designs a special quenching mold, which can effectively ensure the carburizing and quenching quality of thin-walled sleeve teeth parts and control the carburizing and quenching deformation of parts, and the upper pressing die of the quenching mold adopts an integral pressure claw structure evenly distributed along the radial direction to evenly act on the plane of the part, which can well control the flatness, the slope oil guide groove structure of the upper pressing die and the stepped oil guide groove structure of the quenching core mold can realize rapid cooling of the outer wall of the part and stable cooling of the inside, and can well control the roundness of the part. By processing the parts according to the above method, the roundness of the tooth part can be controlled within 0.06mm, the flatness of the end face can be controlled within 0.04mm, the deformation of the parts can be effectively controlled, and the requirements for part processing accuracy can be met. In addition, the carburizing and quenching quality of the parts is stable and the dimensional consistency is good, and the thin-walled sleeve teeth are processed with little or no excess after carburizing and quenching, which not only improves the production and processing efficiency but also saves production costs.

[0076] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0077] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A processing method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth, characterized in that: Includes the following: Carburizing treatment: low-pressure vacuum pulse carburizing is performed on thin-walled sleeve teeth, and then slowly cooled in the furnace after carburizing; Quenching treatment: put the thin-walled sleeve gear into a solid carburizing agent protection box, seal it and then heat it. After heating, quickly put the thin-walled sleeve gear into a cold quenching mold for overall oil spray cooling and quenching. Cold treatment: Continue cooling the thin-walled sleeve gear, keep warm for a preset time, and then air cool; Tempering treatment: The thin-walled sleeve gear is heated at low temperature and kept warm for a preset time, then air-cooled.

2. The method for controlling carburizing and quenching deformation of thin-walled sleeve gear according to claim 1, characterized in that: The carburizing step comprises the following: Place the thin-walled sleeve gear in a vacuum carburizing furnace for low-pressure vacuum pulse carburizing. After evacuation, raise the temperature to 650℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 850℃±10℃, keep it warm for 20 to 30 minutes, then raise the temperature to 930℃±10℃, keep it warm for 30 to 50 minutes, and then start automatic carburizing with acetylene. After carburizing, cool down to ≤100℃ and take it out of the furnace.

3. The method for controlling carburizing and quenching deformation of thin-walled sleeve teeth according to claim 1, characterized in that: The quenching treatment step includes the following contents: Place the thin-walled sleeve gear with the large end facing downward into a solid carburizing agent protection box and seal it. Then heat the protection box in a box-type electric furnace. Keep it at 650℃±10℃ for 35 to 45 minutes, then raise the temperature to 920℃±10℃ with the furnace and keep it for 40 to 60 minutes. Then quickly clamp out the parts one by one and put them into a cold quenching mold. Spray oil on the inner and outer surfaces of the thin-walled sleeve gear on a quenching press to cool and quench. Continue spraying oil until the thin-walled sleeve gear cools to room temperature.

4. The method for controlling carburizing and quenching deformation of thin-walled sleeve teeth according to claim 3, characterized in that: The quenching die comprises an upper die (1), a quenching core die (2), an oil injection base (3), an oil retaining ring (4) and a demoulding base (5). The small end of the upper die (1) is connected and fixed to a lower pressing mechanism of a quenching press. The large end of the upper die (1) is evenly distributed with a plurality of pressing claws (11) along the circumference, which are used to evenly press the middle outer plane of the thin-walled sleeve gear to control the end surface flatness. The oil injection base (3) is connected and fixed to a movable base of the quenching press and is used to communicate with the oil injection circuit of the quenching press. The quenching core mold (2) is connected to the oil injection base (3) to quickly spray out the quenching oil. The quenching core mold (2) is installed on the oil injection base (3), and the thin-walled sleeve gear is sleeved on the quenching core mold (2). The quenching core mold (2) is used to fix the thin-walled sleeve gear, divert the quenching oil and control the roundness of the tooth portion of the thin-walled sleeve gear. The oil retaining ring (4) is installed in the annular groove of the oil injection base (3) to maintain a fixed quenching oil liquid level height so that the thin-walled sleeve gear is completely immersed in the quenching oil. The demoulding base (5) is used to perform demoulding operations.

5. The method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth according to claim 4, characterized in that: An oil injection hole (31) is provided in the middle of the oil injection base (3) and runs through it from top to bottom. A plurality of first oil guide grooves (32) are evenly distributed radially on the middle plane of the oil injection base (3), and the plurality of first oil guide grooves (32) are all connected to the oil injection hole (31). The central inner hole of the quenching core mold (2) is aligned with the oil injection hole (31). During the quenching process, quenching oil is sprayed upward from the oil injection hole (31), a portion of the quenching oil flows out through the plurality of first oil guide grooves (32) and flows to the outside of the thin-walled sleeve gear to cool its outer wall surface, and another portion of the quenching oil is sprayed out through the central inner hole of the quenching core mold (2) and fills the inner cavity of the thin-walled sleeve gear to cool its inner wall surface.

6. The method for controlling carburizing and quenching deformation of thin-walled sleeve gear according to claim 5, characterized in that: The central inner hole of the upper die (1) is aligned with the central inner hole of the quenching core die (2); a plurality of second oil guide grooves (12) inclined downward are evenly distributed along the radial direction on the middle plane of the upper die (1); the number of the second oil guide grooves (12) is the same as the number of the pressing claws (11); and the end position of each second oil guide groove (12) is aligned with the pressing claw (11); part of the quenching oil sprayed from the central inner hole of the quenching core die (2) flows sequentially through the central inner hole of the upper die (1), the plurality of second oil guide grooves (12) and the plurality of pressing claws (11) to the outer wall surface of the thin-walled sleeve tooth, so as to achieve rapid and uniform cooling of the outer wall surface.

7. The method for controlling carburizing and quenching deformation of thin-walled sleeve gear according to claim 5, characterized in that: The upper end surface of the quenching core mold (2) is evenly distributed with a plurality of stepped third oil guide grooves (21) along the radial direction, so that the quenching oil can flow stably along the inner wall surface of the thin-walled sleeve gear, thereby achieving uniform and stable cooling of the inner wall surface of the thin-walled sleeve gear.

8. The method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth according to claim 4, characterized in that: When the thin-walled sleeve gear is cooled to room temperature, the thin-walled sleeve gear and the quenching core mold (2) are taken out, the thin-walled sleeve gear is supported on the upper end surface step of the demoulding base (5), and downward pressure is slowly applied to the top plane of the quenching core mold (2) to withdraw the quenching core mold (2) and complete the demoulding operation.

9. The method for controlling the carburizing and quenching deformation of thin-walled sleeve teeth according to claim 1, characterized in that: The cold treatment step comprises the following contents: After the thin-walled sleeve gear is cooled to room temperature, it is transferred to a low-temperature box that has been pre-cooled to -70°C and kept for 2h to 2.5h before being taken out of the oven and naturally returned to room temperature.

10. The method for controlling carburizing and quenching deformation of thin-walled sleeve gear according to claim 1, characterized in that: The tempering step comprises the following: Place the thin-walled sleeve gear in a pit-type electric furnace and heat it to 270℃±10℃. Keep it warm for 2h~2.5h, then take it out and air cool it.

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